This project investigates how rhesus monkeys and other primate species born and raised under different laboratory conditions adapt to placement into naturalistic outdoor environments and compares this adaptation process to that seen in natural settings and in indoor environments that contain specific physical and social features of the monkeys' natural habitat. Adaptation is assessed by examining behavioral repertoires and by monitoring a variety of physiological systems in these subjects, yielding broad-based indices of relative physical and psychological well-being. During FY91 detailed longitudinal comparisons between middle-aged members of rhesus monkey troop living in a 5-acre outdoor enclosure and same-aged members of a group living in an indoor pen over a comparable period revealed surprising group differences: indoor subjects displayed higher levels of social and exploratory activities than did the subjects living in the outdoor field environment. Remarkable year-to-year stability of individual differences for several behaviors from 6 to 10 years of age was also demonstrated for both groups. Subsequent analyses of the oldest group members revealed significant stability of individual differences in certain behaviors from infancy to 20 years, demonstrating a behavioral continuity over essentially the entire lifespan for the species. Other studies focused on direct comparisons between group-housed rhesus and capuchin monkeys with respect to behavioral repertoires and responses to various environmental enrichment devices. A detailed study comparing vocalization patterns of wild-living capuchin monkeys with those maintained in captivity was continued. The cumulative results of a series of comparative studies of vocalization patterns of wild troops of capuchin monkeys, squirrel monkeys, and gold lion tamarins yielded the general conclusion that most vocalizations produced by these New World monkey species in the wild function to maintain troop cohesion and permit the initiation and coordination of troop movement. Finally, principles gleaned from developing procedures for defining and promoting well-being in captive nonhuman primate species were formally examined for possible insights regarding aspects of physical and social environments that might serve to promote and enhance well-being in human populations.